This relates in general to an automatic drilling system, more particularly for drilling fine holes in thin frangible workpieces such as, for example, watch crystals.
An obvious problem which has arisen with prior art devices of the type described is that the watch crystals, or other frangible plates, tend to be shattered or the hole being drilled tends to breakout during the drilling process. One method used in the prior art of avoiding such breakout is by the additional operation of waxing the bottom of the workpiece, and applying thereto a carbon substrate, for the duration of the drilling operation. Further disadvantages inherent in prior art processes are that they tend to reduce the life of the drill, increasing the expense of the process.
It has been found that the tendency of the workpiece to shatter or breakout is minimized and the life of the drill is maximized by carefully controlling the speed of rotation and frequency and extent of the pecking excursions of the quill during the drilling process. In order to control such an operation manually, a highly skilled operator must give it undeviating attention. If the operator becomes tired or careless, a high rate of broken workpieces results.